Candidate: Dr. Bharat's academic training, research experience and drive place him in an excellent position for a successful career to become a leading independent investigator. He intends to pursue a career in academic surgery with a strong commitment to basic and translational research. He has demonstrated a passion for research as a trainee at Washington University and since his recruitment to Northwestern University. He has already received the prestigious Gibbon Research Scholarship from the American Association of Thoracic Surgery and a Gift of Hope Foundation grant. His lab has generated four abstracts in national meetings and two manuscripts, currently under review, related to the work outlined here. Dr. Bharat completed a prospective clinical trial and took his clinical findings to the laboratory generating strong preliminary data that led to the exciting new hypothesis that forms the basis for this application. These studies have the potential of improving lung healing and outcomes following lung surgery. The K08 program will enable him to expand his research skills by integrating knowledge from inter-related disciplines and become an independent surgeon-scientist, while finding answers to a major clinical problem. Mentors: The Department of Surgery and the Division of Pulmonary and Critical Care Medicine at the Northwestern University are committed to fostering the academic careers of outstanding junior faculty like Dr. Bharat. His mentor Dr. Jacob Sznajder, co-mentors Drs. Harris Perlman and Peter Sporn are well-funded investigators with a long track record of training junior faculty. Thei laboratories have the expertise, tools and resources required to complete the proposed studies. In addition, Dr. Melina Kibbe, surgeon-scientist and Vice Chair for Research and Dr. Malcolm DeCamp, Chief of Thoracic Surgery, are committed to his research development along with the strong institutional support from Northwestern University. Environment: Dr. Bharat will conduct his research training in the Division of Pulmonary and Critical Care Medicine at Northwestern. Strong collaborations between the 13 federally funded investigators in this Division combined with their interactions with Division of Immunology as well as investigators in the Northwestern community and around the world provide an ideal environment for Dr. Bharat to develop into an independent scientist. In addition, the collaboration with the world-class Comprehensive Transplant Center, its state-of-the- art microsurgery center and a number of Northwestern core facilities will facilitate successful conclusion of these studies. The institution has already provided a strong start-up package and protected time to Dr. Bharat. Research: Over 90% of patients undergoing lung surgery will have an air leak from the cut surface of the lung. Removal of apoptotic cells (efferocytosis) at the site of injury and epithelial cell migration is necessaryfor lung repair and resolution of air leaks. Unfortunately up to 50% of patients can demonstrate poor healing that is manifested by prolonged air leak. Prolonged air leak is the major contributor of post-operative mortality after lung surgery. In addition, up to 20% of patients with spontaneous pneumothorax can demonstrate prolonged air leak due to poor lung healing. The pathogenesis of poor lung healing following surgery has not been previously investigated. The studies outlined here originate from our observation in a prospective clinical study of over 120 patients indicating that high concentration of carbon dioxide in the pleural cavity following lung surgery is associated with prolonged air leak. Preliminary data showed that high carbon dioxide suppresses efferocytosis by macrophages as well as epithelial cell migration, leading to delayed wound closure. We propose to investigate the pathways by which hypercarbia suppresses lung repair by the following aims: Aim 1, Determine whether hypercarbia suppresses phagocytosis of apoptotic epithelial cells and CXCL12 production by alveolar macrophages. We will investigate the mechanisms by which hypercarbia suppresses efferocytosis of apoptotic cells by macrophages and production of CXCL12, a chemokine necessary for epithelial cell migration. Aim 2, determine the mechanisms of hypercarbia-induced suppression of Rac1-mediated epithelial cell migration. We will determine how the Rac1-mediated pathway for epithelial cell migration is suppressed by microRNA183 that is upregulated in hypercarbia. Aim 3, Determine whether hypercarbia impairs wound repair in a murine model of epithelial injury. The effects of hypercarbia on macrophages and epithelial cells leading to poor wound healing will be determined using conditional knockout and chimeric mice as well as anti-microRNA (antagomir) therapy.